In 2014, we reported that shadows can be displayed in 3D using a stereoscopic setup. We now report
that the 3D shadows can also be used to perform simple measurements, which are suitable for physics
education in schools and colleges. Two different types of measurements are demonstrated, i.e.
microscopy and vibrometry. Both types of measurements take advantage of the geometrical optics of
the 3D shadows, where the 3D position of an object can be estimated using the coordinates of the
colored light sources and the coordinates of the colored shadow images. We also include several
student activities that can raise the students’ curiosity and capability.